Currently, the internationally promoted electric helicopters are mostly multi-rotor structures. It has been developed from the structure of multi-rotor drones in recent years. For example, the multi-rotor air taxis, the jets in the movie Iron Man and the trapeze. Those aircrafts are unlikely to obtain the flight management department's flight permit because they (even with installed parachutes) do not meet safe landing requirement in the event of a failure of the power system. Those helicopters are not equipped with autorotation landing functions.
An ideal (desirable flying), electric helicopter is made possible because of high energy motors and highly efficient batteries. The helicopter of the present disclosure uses a torque arm assembly with propellers generating power to drive a main rotor assembly.
A traditional helicopter relies on an engine's output energy to rotate a main rotor assembly. The main rotor assembly generates lifting force so that the helicopter takes off. A traditional power drive mode is that the power of an internal combustion engine, a turboshaft engine or an electric motor is decelerated by a gearbox. The torque is increased to drive a large-size main rotor assembly.
For a traditional helicopter, while the main rotor assembly is rotating, the entire fuselage also produces a reaction torque with equivalent magnitude. Therefore, the engine and the fuselage will experience the same torque as the main rotor assembly. A tail rotor with long tail boom system is used to balance this torque. A long tail boom system balances the fuselage so that it maintains the direction of the fuselage and the fuselage does not rotate due to the torque of the main rotor assembly. It is conceivable that the transmission system, the balanced torque tail rotor and the long tail boom system not only consume nearly 20% of the power, but also increase the manufacturing difficulties and control issues. The increased control issues may cause accidents.
Another traditional way to drive the main rotor assembly is that the jet engine mounted at the tip of the main rotor assembly produces thrust force to drive the main rotor assembly to rotate. In this way, there is no torque on the fuselage and no longer needs the tail rotor tail boom and a driving system. But it encounters a new issue. When the main rotor assembly is under rotation, the weight of the engine installed at the tip of the rotor generates huge centrifugal force. The jet output direction of the jet engine will constantly change following the change of the blade angle of the rotor blade. The fuel and control transmit through the center shaft. The rotary shaft is output to the tip of the rotor blade that rotates at a high speed.
Up to now, there are many test models, but there are very few practical models entering the commercial market. An important feature of the present disclosure is that the output shaft of the driving motor aligns with an axis of the main rotor shaft so that the centrifugal force of the driving motor is negligible (almost zero). A timing belt with a center distance of approximately 1 meter drives the tip of the propeller from inside the torque arm to push or pull the main rotor to rotate. The timing belt and the push or pull propellers weigh less than one pound and the centrifugal force is small. The torque is calculated by the thrust force (pulling or pushing the propeller) multiplying the torque arm radius of approximate one meter giving the power torque required for the main rotor in the unit of kg-meter or N-M. Motor power is delivered from the central shaft to the motor. It increases the drive efficiency by 35%. If without tail rotor and drive train, the helicopter's mechanical structure has been simplified by 40%. The driving method of the present disclosure is especially suitable for light and small helicopters. The main rotor of the helicopter is rotated by pushing and pulling of an electric propeller mounted on the tip of the torque arm. Helicopters include torque arm driving system. Applicant's issued U.S. Pat. No. 10,076,763 discloses half-flight and half-walk propeller lift suspension boom truss module system. A new driving method may be applied to a helicopter that uses an electric propeller torque arm as the power to drive the main rotor.